Well cementing

ABSTRACT

A hydraulic cementing composition and a method of making the same is disclosed. The composition is useful to form a sheath of hardened cement in the annular space between a well pipe disposed in a well bore and the walls of the well bore. The cementing composition is a mixture of dry ingredients comprising hydraulic cement and an additive to control the loss of fluid from an aqueous slurry containing the cementing composition. The fluid loss additive and a method of making the same is disclosed. The fluid loss additive is the reaction product of three chemical compounds each having an ethylene backbone and functional groups selected from carboxylates, hydrogen, anhydrides and combinations thereof.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

This invention broadly relates to cementing. The invention furtherrelates to a cement composition for supporting pipe in a borehole whichpenetrates one or more subsurface earth formations. The invention stillfurther relates to an additive included in a hydraulic cementingcomposition. The invention more specifically relates to a copolymeradditive useful to reduce the loss of water from a slurry of hydrauliccement in water.

2. Description of the Prior Art and Problems Solved

It is known in the art of well cementing to form a sheath of hardenedcement in the annular space between a well pipe, such as a casing, andthe walls of a well bore which penetrates a subterranean earthformation. The purpose of the sheath is to support the casing in thewell bore and to prevent undesirable movement of formation fluids, suchas oil, gas and water, within the annular space between subsurfaceformations and/or to the surface of the earth. The process of formingthe sheath is referred to in the art as primary cementing.

In the art of primary cementing, a slurry of hydraulic cement in wateris pumped down the interior of the casing and caused to circulate upfrom the bottom of the casing in the annulus to a desired locationtherein, and then permitted to remain undisturbed in the annulus for atime sufficient to enable the hydraulic cement to react with the waterin the slurry, i.e., set, to produce the sheath of hardened cement.

A slurry of hydraulic cement in water, when first placed in the annulus,and for a period of time thereafter, acts as a true liquid and cantransmit hydrostatic pressure. Loss of water from the slurry to theformation, referred to as fluid loss, causes a reduction in slurryvolume which can cause pressure loss. Gas migration within the settingslurry can occur if pressure loss occurs at a time when the slurry hasgelled to degree which prevents full transmission of hydrostaticpressure.

A slurry of hydraulic cement, over a period of time, sets into ahardened mass having compressive strength. It is believed that thehardening process experiences three phases.

During the first phase of the hardening process, it is believed that thesetting slurry retains liquid sufficient to enable it to transmit fullhydrostatic pressure in the well bore through the column of cementslurry. It is believed that gas migration will not occur if there issufficient transmitted pressure to oppose formation gas pressure. Thefirst phase ends when the developed static gel strength attains a firstcritical value which is believed to be about 100 lb-force/100 sq. ft.The period of time required for a slurry of hydraulic cement to reachthe first critical value is referred to as zero gel time. Zero gel timeis thus defined as the time required for a slurry to develop a staticgel strength of about 100 lb-force/100 sq. ft. During this time, it isbelieved that the volume of fluid lost to the formation will not resultin loss of pressure across a gas zone in an amount sufficient to permitgas migration.

During the second phase of the hardening process, the developed staticgel strength exceeds the first critical value. The setting slurry losesthe ability to transmit full hydrostatic pressure, but fluid losscontinues. As a setting slurry passes from a fluid state to a gelledstate, defined as the transition period, hydrostatic pressure cannot befully transmitted. Accordingly, any loss of fluid volume during thetransition period will cause loss of pressure across a gas zone, whichcould result in gas migration. The second phase ends when the developedgel strength attains a second critical value which is sufficient toresist formation gas pressure. It is believed that the second criticalvalue is about 500 lb-force/100 sq. ft. The purpose of a fluid lossadditive is to provide fluid loss control during the transition period.It is desired that the transition time be as short as possible.

During the third phase of the hardening process gas migration isprevented if a gas channel has not been previously formed, becausedeveloped gel strength is greater than the second critical value and issufficient to resist formation gas pressure.

It is desirable to extend zero gel time and to reduce transition time.The loss of fluid from a slurry of hydraulic cement in water increaseswith increase in bottom hole circulating temperature. Accordingly, amaterial to be added to a slurry of hydraulic cement to extend zero geltime and to reduce transition time, while reducing fluid loss rate athigh temperatures, is a problem addressed herein.

Laramay et al (U.S. Pat. No. 6,089,318) discuss problems caused by fluidloss. Such problems include gas migration, the development of inadequatestatic gel strength, and the formation of channels in the sheath ofcement. The discussion is included herein by reference.

Laramay et al disclose a composition which reduces fluid loss from aslurry of hydraulic cement in water at temperatures up to 400° F. andparticularly above 200° F. The composition disclosed by Laramay et al isthe copolymerization reaction product of a vinylamide morpholinederivative with a styrene sulfonic acid salt, when performed in thepresence of a humate. The preferred vinylamide morpholine derivative isacryloylmorpholine. The preferred styrene sulfonic acid is sodiumstyrene sulfonate. The humate employed is potassium humate.

Laramay et al further disclose that acrylamide and derivatives ofacrylamide can be employed along with the previously mentionedcomponents to produce the composition of their invention. Examples ofsuch optional compounds mentioned by Laramay et at include acrylamide,the sodium salt of 2-acrylamido-2-methylpropanesulfonic acid andN,N-dimethylacrylamide.

It is known in the art that a slurry of hydraulic cement is comprised ofparticles of a hydraulic cement suspended or dispersed in water. Theslurry can also include various added materials, for example, fluid lossadditives, dispersants, suspension agents, strength stabilizing agents,set time retarders, set time retarder intensifiers and defoamers.

A slurry of hydraulic cement in water can be caused to flow, such aswith pumping equipment, down a well pipe and then upwardly into anannular space where it is permitted to remain static while it sets intoa hardened sheath. The study of the ability of a slurry of hydrauliccement in water to flow is included in a term broadly referred to asrheology, which, in large part, is concerned with the flow of matter inthe liquid phase. Such liquids can be classed as either Newtonian fluidsor as non-Newtonian fluids. A non-Newtonian fluid exhibits an apparentchange in viscosity with rate of change of strain (strain rate). Aslurry of hydraulic cement in water is a non-Newtonian fluid.

A rheological property of a slurry of hydraulic cement in water which isof particular interest to persons skilled in the art of well cementingis the ability of the slurry to suspend the particles of cement in thefluid. The rheological properties must be adequate to suspend solids atsurface conditions during mixing, and also at down hole temperature andpressure. The goal is to prevent solids settling and bridging whilepumping. Instruments employed to measure this settling property providenumerical readings at various shear rates (measured in rpm). As ageneral rule, higher numerical readings indicate satisfactory suspensionand lower readings indicate less satisfactory to unacceptablesuspension. A combination of materials added to a slurry can benecessary to provide a slurry having low water loss, as well assatisfactory solids suspension and acceptable pumping time.

Consistency is a rheological property of a fluid which is related tocohesion of individual particles of a material in the fluid, such as theparticles of cement in the slurry, the ability of the fluid to deformand its resistance to flow. The consistency of a cement slurry isdetermined by thickening time tests and is a measure of the ability ofthe slurry to be pumped. Consistency is, accordingly, a measure of thepumpability of the slurry.

It is clear that the slurry must contain a sufficient quantity of waterto enable sufficient hydration of the cement particles. In addition,there must be a sufficient quantity of water in the slurry to enable itto be pumped, but not so much that the consistency (sometimes known asapparent viscosity) of the slurry is not sufficient to retain theparticles of cement in suspension during the hardening process.

Rheology, including consistency, is effected by fluid loss. Fluid losscan be adjusted by materials added to a cementing composition. Suchmaterials include fluid loss additives, suspending agents anddispersants. This invention, accordingly, further addresses cementingcompositions comprised of fluid loss additives, dispersants andsuspending agents.

SUMMARY OF THE INVENTION

This invention provides a cementing composition which is useful to forma sheath of hardened cement in the annular space between a well pipedisposed in a well bore and the walls of the well bore. The cementingcomposition is a mixture of dry ingredients comprising hydraulic cement,a fluid loss additive and one or more other additive materials. When thecementing composition is mixed with water a slurry is produced which canbe pumped into the mentioned annular space, which can suspend solidparticles while the slurry sets into a hardened mass, and which provideslow fluid loss from the slurry at temperatures up to about 400° F.

The invention also provides a method of making the cementing compositionand the mentioned pumpable slurry containing the cementing composition.

The invention further provides a material which is added to thecementing composition to control the loss of fluid from the slurrycontaining the cementing composition. The material is hereinafterreferred to as the fluid loss additive of this invention.

The fluid loss additive of this invention is the reaction product of anumber of chemical compounds each having an ethylene backbone andfunctional groups selected from carboxylates, such as sodiumcarboxylate, hydrogen, anhydrides and combinations thereof.

The invention still further provides a method of making the fluid lossadditive of this invention.

DESCRIPTION OF THE INVENTION

1. Fluid Loss Additive

It has now been discovered that reacting a first compound, a secondcompound and a third compound in the presence of an effective quantityof a humate produces a product which can be used as a fluid lossadditive for a hydraulic cementing composition. The fluid loss additiveis water soluble and can be added to a hydraulic cement composition insolution form or in solid form.

The first compound is a sulfonic acid acrylic monomer selected fromcompounds represented by the general formula:CH₂═CR₁—C(═O)—NR₂R₃  (1)wherein R₁ is —H or —CH₃; R₂ is —H, —CH₃ or —CH₂CH₃; and R₃ is—C(CH₃)₂—CH₂S(═O)₂—OX, wherein X is —H or —NH₄ or is selected from Group1A metals such as —Na.

Examples of the sulfonic acid acrylic monomer defined in formula (1)include 2-acrylamido-2-methylpropanesufonic acid, the sodium salt of2-acrylamido-2-methylpropanesufonic acid and the ammonium salt of2-acrylamido-2-methylpropanesufonic acid.

The second compound is acrylamide, an acrylamide derivative or avinylamide morpholine derivative.

The acrylamide and acrylamide derivative is selected from compoundsrepresented by the general formula:CH₂═CR₄—C(═O)—NR₅R₆  (2)wherein R₄ is —H or —CH₃; R₅ is —H, —CH₃ or —CH₂CH₃; and R₆ is —H, —CH₃,—CH₂CH₃, —CH(CH₃)₂ or —C(CH₃)₃.

Examples of the compounds defined in formula (2) include acrylamide,methacrylamide, N-methylacrylamide, N-i-propylacrylamide,N-i-propylmethacrylamide, N-t-butylacrylamide, N-t-butylmethacrylamide,N,N-dimethylacrylamide and N,N-dimethylmethacrylamide.

The vinylamide morpholine derivative is selected from compoundsrepresented by the general formula:

wherein R₇ is —H or —CH₃ and R₈ is —H, —CH₃ or —CH₂CH₃ and is positionedon any one of the four carbons in the morpholine ring.

Examples of the vinylamide morpholine derivative defined in formula (3)include acryloylmorpholine and methacryloylmorpholine.

The third compound is an ethylene derivative having terminal endsselected from carboxylic acid groups, carboxylate groups, such as sodiumcarboxylate, hydrogen, anhydride groups and combinations thereof. Thethird compound is selected from compounds represented by the generalformula:R₉R₁₁C═CR₁₀R₁₂  (4)wherein: R₉ is —C(═O)OH, —C(═O)ONa, or —CH₂C(═O)OH; R₁₀ is, —C(═O)OH or—H; R₁₁ is —C(═O)OH or —H and R₁₂ is —H; or R₉ and R₁₀ are each carbonylgroups joined to oxygen to form an anhydride group, —C(═O)—O—C(═O)—.

Some compounds within the scope of formula (4) include maleic acid,fumaric acid, acrylic acid, sodium acrylate, itaconic acid and maleicanhydride.

The preferred first compound is the sodium salt of2-acrylamido-2-methylpropanesufonic acid. The preferred second compoundis N,N-dimethylacrylmide. The preferred third compound is maleicanhydride.

The term humate, as used herein, is a generalization for any naturallyoccurring derivative of humic acid. Humic acids are allomelanins foundin soils, coals and peat resulting from the decomposition of organicmatter, particularly dead plants, and consist of a mixture of complexmacro molecules having a polymeric phenolic structure. A humate usefulherein is available from Black Earth Humic LP under the trademarkBlackEarth As used herein the quantity of humate employed is expressedas a quantity of potassium humate.

The method of copolymerizing the first, second and third compounds toproduce the fluid loss additive of this invention is broadly comprisedof the steps of forming an aqueous medium having the humatedispersed/dissolved therein, dissolving the monomer reactants in theaqueous medium and then causing the monomer reactants to produce thefluid loss additive of this invention. As a final optional step, thefluid loss additive, which is present in solution in the reaction mass,can be recovered as a dry, particulate solid for further use as a dryadditive for a hydraulic cement composition.

In the first step, a first aqueous medium is formulated by mixing waterwith an aqueous solution of sodium hydroxide followed by mixing thehumate with the resulting solution. Water is placed in the first aqueousmedium in an amount in the range of from about 31 to about 85 andpreferably about 52 weight percent of the entire reaction mass. Thewater is preferably D.I, water. The aqueous solution of sodium hydroxideis placed in the first aqueous medium in an amount in the range of fromabout 1.3 to about 1.7 and preferably about 1.5 weight percent of theentire reaction mass, wherein the sodium hydroxide solution containsabout 50 weight percent sodium hydroxide. Humate is placed in the firstaqueous medium in an amount in the range of from about 1 to about 11 andpreferably about 6 weight percent of the entire reaction mass, whereinthe humate is calculated as 12 percent by weight active potassiumhumate.

The first aqueous medium is stirred for a short time to insure completemixing/dispersion of the contents, thereafter the monomer reactants,that is, the above described first compound, second compound and thirdcompound, are added, in sequence, to the first aqueous medium withstirring. The monomer reactants are added to the first aqueous medium ina combined quantity in the range of from about 26 to about 52 andpreferably about 38 weight percent of the entire reaction mass. Thefirst and second and compounds are present in the reaction mass in therange of from about 1.5 to about 2.5, preferably from about 1.6 to about2.1 and still more preferably about 1.8 moles of the first compound permole of the second said compound. The first and third and compounds arepresent in the reaction mass in the range of from about 4.8 to about9.8, preferably from about 6.1 to about 7.8 and still more preferablyabout 7.5 moles of the first compound per mole of the third compound.After all of the monomer reactants are completely dissolved, the pH ofthe mix is adjusted, such as with caustic soda, to a value in the rangeof from about 8 to about 10.5, preferably about 9, to thereby form asecond aqueous medium. Stirring continues and the temperature of thesecond aqueous medium is heated to a reaction temperature of about 114°F.

Activator ingredients are added to the second aqueous medium to causethe polymerization reaction to proceed. The activator ingredientsinclude water, a chain transfer agent and a polymerization initiator tothereby complete the entire reaction mass. The activator ingredients areadded to the second aqueous medium in a combined quantity in the rangeof from about 3.1 to about 4.3 and preferably in an amount of about 3.8weight percent of the entire reaction mass. The chain transfer agent isadded to the second aqueous medium in an amount of about 0.01 weightpercent of the entire reaction mass and the polymerization initiator isadded to the second aqueous medium in an amount in the range of fromabout 0.39 to 0.60, and preferably in an amount of about 0.46 weightpercent of the entire reaction mass. The water constituent of theactivator ingredients is preferably divided into about two equal weightportions each of which are added to the second aqueous medium to therebyform the entire reaction mass.

The temperature of the reaction mass increases upon addition of theactivator ingredients to the second aqueous medium. The temperature ofthe water bath is adjusted to maintain the reaction temperature at avalue of about 140° F. which such temperature is maintained for 2 hourswhile stirring continues.

The chain transfer agent can be tetraethylenepentamine, mercaptoethanoland sodium allylsulfonate.

The polymerization initiator can be initiators known in the artincluding sodium persulfate, potassium perborate and ammoniumpersulfate.

After completion of the 2 hour polymerization reaction, the reactionmass can be diluted with water and then dried to produce a solid productwhich is useful as the fluid loss additive of this invention. The dryingprocess can include the steps of placing the liquid reaction mass on therollers of a drum dryer to form a dry polymer product.

2. Hydraulic Cement Composition

It has been discovered that a dry hydraulic cement compositioncontaining the fluid loss additive of this invention, when mixed witheither fresh or salt water, produces a slurry which can be pumped, whichhas acceptable solids suspension and which has low fluid loss attemperatures up to 400° F. The dry hydraulic cement composition of thisinvention is comprised of hydraulic cement and the fluid loss additiveof this invention. The dry composition can also include various otheradditives including dispersants, suspension agents, strength stabilizingagents, set time retarders, set time retarder intensifiers anddefoamers.

The term “hydraulic cement” includes compounds of a cementitious naturewhich set in the presence of water. Such compounds include, for example,Portland Cement, in general, and particularly Portland Cement of APIClasses G and H, although other API classes can be used. Other usefulhydraulic cements include pozzolan cements, gypsum cements, high aluminacontent cements, slag cements, high gel cements, silicate cements,ultrafine cements and high alkalinity cements. Portland cements, andparticularly API Classes G and H, are preferred.

The fluid loss additive of this invention, which is made as abovedescribed, is present in the cementing composition of this invention inan amount in the range of from about 0.1 to about 2.0 and preferablyfrom about 0.3 to about 0.7 pounds of fluid loss additive per 100 poundsof hydraulic cement.

A set time retarder can be employed as an additive when the bottom holecirculating temperature exceeds 100 degrees F. Examples of retarderswhich can be used include lignosulfonates, such as calciumlignosulfonate and sodium lignosulfonate. A set time retarder can bepresent in the cementing composition in an amount in the range of fromabout 0 to about 3.0 and preferably from about 0.15 to about 1.5 poundsof set time retarder per 100 pounds of hydraulic cement.

The function of a set time retarder can be enhanced by a cement set timeretarder intensifier, examples of which include organic acids and saltsthereof. Examples of such acids include citric acid, tartaric acid,gluconic acid and mixtures thereof. A set time retarder intensifier canbe present in the cementing composition in an amount in the range offrom about 0 to about 1.5 pounds of set time retarder intensifier per100 pounds of hydraulic cement.

A strength stabilizing agent can be employed as an additive in thecementing composition of this invention. Examples of strengthstabilizing agents which can be used include silica flour and silicasand. A strength stabilizing agent can be present in the cementingcomposition in an amount in the range of from about 0 to about 100 andpreferably about 35 pounds of strength stabilizing agent per 100 poundsof hydraulic cement.

A dispersant can be employed as an additive in the cementing compositionof this invention. Naphthalene sulfonate is an example of a materialwhich can be used as a dispersant. Lignosulfonates, can also function asdispersants. A dispersant can be present in the cementing composition inan amount in the range of from about 0 to about 1.0 pound of dispersantper 100 pounds of hydraulic cement.

A suspension agent can be employed in the cement composition to helpmaintain a uniform dispersion of solid particles in the slurry of cementcomposition in water during pumping and setting. Examples of suspensionagents include bentonite, water soluble polymers, cellulose derivatives,silicates, welan gum, diutan gum and mixtures of welan and/or diutanwith silica flour. A suspension agent can be present in the cementingcomposition in an amount in the range of from about 0 to about 8.0pounds of suspension agent per 100 pounds of hydraulic cement.

The cement composition may also include foaming agents or defoamingagents which comprise various anionic, cationic, nonionic or othersurface active compounds. One specific surface active agent which can beemployed herein as a defoaming agent is polypropylene glycol. The amountof surface active agent can be present in the range of from about 0 toabout 3 and preferably from about 0.1 to about 0.3 pounds of surfaceactive agent per 100 pounds of cement.

3. Slurry of Hydraulic Cement Composition in Water

The above described dry ingredients are mixed to form the hydrauliccement composition of this invention which can be stored for later use.The dry resulting composition is combined with water to form a pumpableslurry. The amount of water used to mix with the dry composition to makethe slurry can be expressed as pounds of water per 100 pounds of cementand also as pounds of water per 100 pounds of dry composition.Accordingly, the amount of water present in the slurry is an amount inthe range of from about 32 to about 125 and preferably from about 38 toabout 52 pounds of water per 100 pounds of cement. Alternatively, theamount of water present in the slurry is an amount in the range of fromabout 24 to about 45 pounds of water per 100 pounds of dry cementcomposition.

Water used to make the slurry can include a dissolved inorganic salt,such as sodium chloride, in an amount of up to about 38 pounds of sodiumchloride per 100 pounds of water.

EXAMPLES

Co-polymer compositions were prepared with ingredients which areidentified in Table A.

TABLE A Molecular Item Ingredient Definition Function Weight 1 D.I.Water de-ionized water diluent, 18.01 reaction medium 2 NaOH sodiumhydroxide, base 40.00 50% aqueous solution neutralizer 3 K Humatepotassium humate, molecular 258.35 12% active weight control 4 ATBS2-acrylamido-2-methyl- monomer 229.23 propanesulfonic acid, reactant 50%aqueous solution (sodium salt) 5 NNDMA N,N-dimethylacrylamide monomer99.13 reactant 6 ACMO acryloylmorpholine monomer 141.17 reactant 7 ACRacrylamide monomer 71.08 reactant 8 MAA maleic anhydride monomer 98.06reactant 9 TEPA tetraethylenepentamine chain transfer 189.3 agent 10  SPsodium persulfate polymerization 238.1 initiator 11  Caustic sodiumhydroxide pH adjustment 40.00 soda

Example 1

Co-polymer compositions were prepared. A reaction vessel having asuitable capacity and being equipped with a mechanical stirrer and athermometer was employed to prepare each composition. The ingredientsemployed are defined in Table A and the quantities of each ingredientused to prepare each composition are set forth in Tables 1.1, 1.2 and1.3.

TABLE 1.1 Fluid Loss Additive Composition 1 (FLA 1) MOLE MOLES QUANTITYWEIGHT MOLES percent ATBS ITEM INGREDIENT grams percent (active)(active) PER MOLE 1 D.I. Water 92,898.80 51.61 0.000 2 NaOH 2,728.681.52 0.000 3 K Humate 9,905.75 5.50 0.0000 4 ATBS 58,908.78 32.73 128.4959.3213 1.0000 5 NNDMA 7,043.92 3.91 71.06 32.8070 1.8082 6 MAA 1,672.340.93 17.05 7.8717 7.5361 7 D.I. Water 2,732.32 1.52 0.0000 8 TEPA 10.930.01 0.0000 9 D.I. Water 3,278.78 1.82 0.0000 10 SP 819.70 0.46 0.0000Totals 180,000.00 100.00 216.60 100.0000Experimental Procedure for Making FLA 1

Items 1, 2 and 3 of Table 1.1 were added, in sequence, to the reactionvessel. The stirrer was activated and the contents of the vessel werestirred for five minutes. Thereafter, ingredients 4, 5 and 6 were added,in sequence, to the vessel while stirring continued. Stirring continueduntil all solids were dissolved. The pH of the solution was adjusted toa value of 9 with caustic soda. Stirring continued and the contents ofthe vessel were heated to 114° F. in a water bath. Thereafter items 7,8, 9 and 10 were added to the vessel. The temperature of the contents ofthe vessel increased. The temperature of the water bath was adjusted to140° F. and maintained at that level for 2 hours while stirringcontinued.

The reaction mass was dried to produce a solid product. The dryingprocess included the steps of pumping the liquid reaction mass onto therollers of a drum dryer which had been heated by steam to a temperatureequal to the boiling point of water. Liquid in the reaction massevaporated to thereby form a dry polymer product on the rollers of thedrum. The dried polymer product was scraped off of the rollers to formflakes which were then milled to a powder. The powder was subsequentlyemployed as a fluid loss additive as hereinafter described.

TABLE 1.2 Fluid Loss Additive Composition 2 (FLA 2) MOLE MOLES QUANTITYWEIGHT MOLES percent ATBS ITEM INGREDIENT pounds percent (active)(active) PER MOLE 1 D.I. Water 820.12 50.24 2 K Humate 168.80 10.34 3ATBS 499.53 30.60 1.090 53.2487 1.0000 4 ACMO 35.59 2.18 0.252 12.31074.3254 5 ACR 50.12 3.07 0.705 34.4406 1.5461 6 D.I. Water 24.13 1.48 7TEPA 0.37 0.02 8 D.I. Water 28.96 1.77 9 SP 4.90 0.30 Totals 1632.50100.00 2.047 100.000Experimental Procedure for Making FLA 2

Items 1 and 2 of Table 1.2 were added, in sequence, to the reactionvessel. The stirrer was activated and the contents of the vessel werestirred for five minutes. Thereafter, ingredients 3, 4 and 5 were added,in sequence, to the vessel while stirring continued. Stirring continueduntil all solids were dissolved. The pH of the solution was adjusted toa value of 9 with caustic soda. Stirring continued and the contents ofthe vessel were purged with nitrogen and heated to 114° F. in a waterbath. Thereafter items 6, 7, 8 and 9 were added to the vessel. Thetemperature of the contents of the vessel increased. The temperature ofthe water bath was adjusted to 140° F. and maintained at that level for2 hours while stirring continued.

The reaction mass was dried to produce a solid product. The dryingprocess included the steps of pumping the liquid reaction mass onto therollers of a drum dryer which had been heated by steam to a temperatureequal to the boiling point of water. Liquid in the reaction massevaporated to thereby form a dry polymer product on the rollers of thedrum. The dried polymer product was scraped off of the rollers to formflakes which were then milled to a powder. The powder was subsequentlyemployed as a fluid loss additive as hereinafter described.

TABLE 1.3 Fluid Loss Additive Composition 3 (FLA 3) MOLE MOLE QUANTITYWEIGHT MOLES percent ATBS ITEM INGREDIENT grams percent (active)(active) PER MOLE 1 D.I. Water 1369.63 48.92 2 NaOH 40.32 1.44 3 KHumate 292.04 10.43 4 ATBS 868.46 31.02 1.894 59.312 1.0000 5 NNDMA103.88 3.71 1.048 32.819 1.8073 6 MAA 24.64 0.88 0.251 7.870 7.5368 7D.I. Water 40.29 1.44 8 TEPA 0.17 0.01 9 D.I. Water 48.40 1.73 10 SP12.04 0.43 Totals 2799.87 100.00 3.193 100.000Experimental Procedure for Making FLA 3

Items 1, 2 and 3 of Table 1.3 were added, in sequence, to the reactionvessel. The stirrer was activated and the contents of the vessel werestirred for five minutes. Thereafter, ingredients 4, 5 and 6 were added,in sequence, to the vessel while stirring continued. Stirring continueduntil all solids were dissolved. The pH of the solution was adjusted toa value of 9 with caustic soda. Stirring continued and the contents ofthe vessel were heated to 114° F. in a water bath. Thereafter items 7,8, 9 and 10 were added to the vessel. The temperature of the contents ofthe vessel increased. The temperature of the water bath was adjusted to140° F. and maintained at that level for 2 hours while stirringcontinued.

The reaction mass was dried to produce a solid product. The dryingprocess included the steps of pumping the liquid reaction mass onto therollers of a drum dryer which had been heated by steam to a temperatureequal to the boiling point of water. Liquid in the reaction massevaporated to thereby form a dry polymer product on the rollers of thedrum. The dried polymer product was scraped off of the rollers to formflakes which were then milled to a powder. The powder was subsequentlyemployed as a fluid loss additive as hereinafter described.

Cementing compositions were prepared with ingredients which areidentified in Table B.

TABLE B Ingredient Chemical Definition Function Class H Hydraulic cementbasic well cement for use from cement API Spec. 10 surface to 8000 feetClass G Hydraulic cement basic well cement for use from cement API Spec.10 surface to 8000 feet SSA-1 Silica flour strength stabilizing agentSSA-2 Silica sand strength stabilizing agent CLS Calcium lignosulfonatecement set time retarder TTA Tartaric acid cement set time retarderintensifier SG Sodium gluconate cement set time retarder intensifier SADry blend, 80 wt. parts diutan suspension agent gum, 240 wt. partssilica flour DSP Naphthalene sulfonate dispersant NaCl Sodium chlorideincrease salt content of water DFMR Polypropylene glycol defoamer FLASee Tables 1, 2 and 3 fluid loss additive

Example 2

Cement compositions were prepared by mixing water with dry ingredients.The dry ingredients, water and the quantities of each are set forth inTables 2.1, 2.2, 2.3, 2.4 and 2.5.

TABLE 2.1 CEMENT COMPOSITION INGRE- grams DIENT 1 2 3 4 5 6 7 Cement600.00 600.00 600.00 600.00 600.00 600.00 600.00 Class H SSA-1 210.00210.00 210.00 210.00 210.00 SSA-2 210.00 210.00 FLA 1 1.80 1.80 3.004.20 FLA 2 1.80 1.80 4.20 CLS 7.20 7.20 7.20 7.20 7.20 7.20 7.20 TTA3.60 3.60 3.60 3.60 3.60 3.60 3.60 SA 0.60 0.60 0.90 0.60 0.60 0.60 0.90TOTAL 823.20 823.20 823.50 823.20 824.40 825.60 825.90 dry ingre- dientsD.I. 228.00 228.00 313.83 313.83 313.83 313.83 313.83 Water TOTAL1051.20 1051.20 1137.33 1137.03 1138.23 1139.43 1139.73 slurry ingre-dients

TABLE 2.2 CEMENT COMPOSITION INGRE- grams DIENT 8 9 10 11 12 13 14Cement 850.00 850.00 850.00 850.00 850.00 850.00 850.00 Class H FLA 12.55 2.55 2.55 2.55 2.55 FLA 2 2.55 2.55 DSP 4.25 3.40 2.13 2.13 4.254.25 CLS 1.70 1.28 1.28 1.28 1.28 1.28 1.28 SA 0.85 0.85 TOTAL 854.25858.08 857.23 855.96 855.96 858.93 858.93 dry ingre- dients D.I. 324.02324.02 324.02 324.02 324.02 324.02 324.02 Water TOTAL 1178.27 1182.101181.25 1179.98 1179.98 1182.95 1182.95 slurry ingre- dients

TABLE 2.3 CEMENT COMPOSITION grams INGREDIENT 15 16 17 Cement 850.00850.00 850.00 Class H FLA 1 2.89 FLA 2 2.89 2.89 SA 0.43 TOTAL 852.89852.89 853.32 dry ingredients D.I. Water 324.02 324.02 324.02 TOTAL1176.91 1176.91 1177.34 slurry ingredients

TABLE 2.4 CEMENT COMPOSITION grams INGREDIENT 18 19 20 21 22 23 Cement600.00 600.00 600.00 600.00 Class H Cement 600.00 600.00 Class G SSA -2210.00 210.00 210.00 210.00 210.00 210.00 FLA 3 0.00 1.80 1.80 3.00 3.001.80 CLS 7.20 7.20 7.20 7.20 7.20 7.20 TTA 3.60 3.60 3.60 3.60 3.60 3.60SA 1.20 1.20 1.20 1.20 1.20 1.20 NaCl 41.04 84.70 DFMR 0.60 0.60 TOTALdry 822.00 823.80 823.80 825.00 866.64 909.10 ingredients D.I. Water228.00 228.00 264.00 264.00 228.00 228.00 TOTAL slurry 1050.00 1051.801087.80 1089.00 1094.64 1137.10 ingredients

TABLE 2.5 CEMENT COMPOSITION grams INGREDIENT 24 25 26 27 28 Cement600.00 850.00 850.00 640.00 640.00 Class H SSA-2 210.00 SSA-1 224.00224.00 FLA 1 3.20 5.12 FLA 2 3.00 4.25 4.25 DSP 4.25 CLS 7.20 1.28 3.363.36 TTA 3.60 SG 1.12 1.12 SA 0.60 0.85 TOTAL 824.40 860.63 854.25871.68 873.60 dry ingredients D.I. Water 228.00 324.02 324.02 307.52307.52 TOTAL 1052.40 1184.65 1178.27 1179.20 1181.12 slurry ingredients

Example 3

Fluid loss and rheology tests were conducted on the hydraulic cementslurries described in Tables 2.1, 2.2, 2.3, 2.4 and 2.5.

Fluid Loss Test . . . Experimental Procedure

An Atmospheric Consistometer Model 1200, available from OFI TestingEquipment, Inc., of Houston, Tex., comprising a fluid loss jacket and afluid loss cell were preheated to the required temperature. The requiredtemperatures are specified in Tables 3.1, 3.2 and 3.3.

Slurry Preparation

A weighed quantity of each dry ingredient to be included in a cementcomposition to be tested was placed in a dry container. The containerwas closed. The dry contents of the container were uniformly blended byrotating the closed container for about 45 seconds. The temperature ofthe blended dry ingredients was about 73 degrees F. The identities andquantities of the dry ingredients placed in the container for blendingare provided in Tables 2.1, 2.2, 2.3, 2.4 and 2.5.

A weighed quantity of D.I, water to be included in a cement compositionto be tested was placed in the container of an OFITE Model 20 constantspeed blender available from OFI Testing Equipment, Inc., of Houston,Tex. The temperature of the D.I. water placed in the container was about73 degrees F. The quantity of water for each composition tested isprovided in Tables 2.1, 2.2, 2.3, 2.4 and 2.5.

The container of water was placed on the base of the constant speedblender. The blender was activated and operated at a speed of 4000 rpm.As soon as the blender was activated the blended dry ingredients wereadded to the water in the container at an even pour rate. The entireamount of blended ingredients were added to the water within about 15seconds.

The mixing speed of the blender was increased to 12000 rpm, and thecontents of the container were mixed for 35 seconds. During the 35second mixing period the interior of the container was scraped to ensurethat the entire contents of the container were mixed.

Mixing was terminated. The contents of the container, a slurry of cementcomposition in water, was ready for conditioning.

Slurry Conditioning

The prepared cement slurry was poured into the cup of the atmosphericconsistometer to the depth of the mark fixed on the cup.

A clean, dry consistometer paddle was placed in the cup containing theslurry. The cup and paddle were then connected to the consistometerwhich had been preheated to the test temperature.

The slurry was conditioned for a period of 20 minutes by causing the cupto rotate at 150 rpm around the paddle which was connected to theconsistometer by a torsion spring. The conditioning of the slurry wascommenced within 1 minute of the completion of the preparation of theslurry. The initial consistency, as indicated by the consistometer dial,was recorded. The final consistency was recorded at the end of the 20minute period.

Fluid Loss Tests Up to 200° F.

Fluid loss tests at temperatures less than the boiling point of water upto 200° F. were performed employing the OFITE HTHP filter press model170-00-2 available from OFI Testing Equipment, Inc., of Houston, Tex.The filter press consists of a nitrogen manifold, a high-pressure testcell having removable screens, a heating jacket, a manifold block and asuitable stand.

The nitrogen manifold included a primary pressure regulator and gauge, anitrogen source pressure gauge, a back pressure regulator and gauge, anda manifold block which was connected to the primary pressure regulator.The test cell was comprised of a cylinder having an open top, an openbottom, a top cell cap, a top screen positioned below the top cell cap,a bottom cell cap, a bottom screen positioned above the bottom cell cap,an inlet valve stem connected to the manifold block and an outlet valvestem. An empty dry graduated cylinder was placed under the outlet valvestem at the bottom of the jacket.

The described press components were assembled with the top being leftopen. A cement slurry, having been conditioned no less than 6 minutesprior to testing and at the required temperature, was poured into theopen top of the fluid loss cell. The top cell cap was fixed to the opentop of the fluid loss cell after the slurry attained a level about 0.5inches below the rim of the fluid loss cell.

The filled fluid loss cell was then placed in the pre-heated fluid lossjacket.

A nitrogen supply hose was attached to the hollow stem of the top cellcap which extended above the top of the jacket.

Nitrogen, at 1000 psi, was then admitted to the top cell cap via thenitrogen source on the nitrogen manifold and, simultaneously, the valveon the stem at the bottom of the jacket was opened and a timer wasactivated.

Fluid was forced by the pressured nitrogen out of the slurry through a325 mesh screen and was collected in a cylinder. The quantity of fluidcollected in the cylinder was recorded after 30 minutes, at which timethe test was terminated.

The quantity of fluid collected was doubled. The result was reported asAPI Fluid Loss in cc per 30 minutes.

If the test sample is dehydrated before the elapse of 30 minutes or thetest is terminated before the elapse of 30 minutes, then the fluid lossin 30 minutes, Q₃₀, is estimated by use of a formula provided in API RP10B-2 as follows:Q ₃₀ =Q _(t)*5.447/t ^(1/2)

wherein

-   -   Q₃₀ is the estimated quantity of fluid collected in 30 minutes    -   Q_(t) is the quantity of fluid collected in time t    -   t is the time in minutes when the test ended        In this instance the API fluid loss reported is the estimated        value multiplied by two.

Fluid Loss Tests Greater than 200° F.

Fluid loss tests at temperatures greater than 200° F. were performedemploying the OFITE Stirred Fluid Tester model 120-70 available from OFITesting Equipment, Inc., of Houston, Tex.

After the slurry was prepared, it was poured into the stirring fluidloss cell to a level just above the paddle. The lid on the cell wastightened and the cell was placed in the heating jacket and securedtherein. The paddle was then actuated to stir the slurry at 150 rpm.Pressure at psi was applied at the top of the cell and a thermocouplewas inserted in the cell. The slurry in the cell was heated to the testtemperature, 350° F., and, thereafter, maintained at that level. Theslurry was stirred for an additional twenty minutes after the testtemperature was obtained. Thereafter, stirring was terminated, theheating jacket (and cell) was repositioned, the pressure at the top ofthe cell was set at 1150 psi and the pressure at the bottom of the cellwas set at 150 psi to thereby establish a differential of 1000 psi. Thevalve at the bottom of the cell was opened to permit release of theslurry which passed through a 325 mesh screen and a timer was started.Filtrate passing through the screen was collected in a suitablecontainer. The test was terminated when about 100 cc of filtrate wascollected. The collection time was then recorded. The quantity offiltrate was then multiplied by a factor of two.

If the test sample is dehydrated before the elapse of 30 minutes or thetest is terminated before the elapse of 30 minutes, then the fluid lossin 30 minutes, Q₃₀, is estimated by use of a formula provided in API RP10B-2 as follows:Q ₃₀=Q_(t)*5.447/t ^(1/2)

wherein

-   -   Q₃₀ is the estimated quantity of fluid collected in 30 minutes    -   Q_(t) is the quantity of fluid collected in time t    -   t is the time in minutes when the test ended        In this instance the API fluid loss reported is the estimated        value multiplied by two.        Fluid Loss Test Results

Table 3.1 contains results of fluid loss tests conducted on 26 cementingcompositions. Compositions 1-17 and 19-26 did contain a fluid lossadditive. Composition 18 did not contain a fluid loss additive. Thefluid loss additives included in the cementing compositions aredescribed in Tables 1.1, 1.2 and 1.3. The fluid loss tests wereconducted at three test temperatures, specifically, 350° F., 180° F. and80° F.

TABLE 3.1 API Fluid Loss Fluid loss Additive Cement cc/30 min percent byweight of cement Table Comp. 350° F. 180° F. 80° F. FLA 1 FLA 2 FLA 3 02.5 26 37 0.5 2.3 15 40 0.34 2.3 16 53 0.34 2.4 22 53 0.5 2.4 20 62 0.32.1 6 68 0.7 2.4 21 70 0.5 2.4 22 70 0.5 2.2 9 73 0.3 2.3 17 78 0.34 2.525 78 0.5 2.4 19 80 0.3 2.4 19 81 0.3 2.4 19 84 0.3 2.1 7 88 0.7 2.2 1388 0.3 2.1 1 90 0.3 2.5 24 91 0.5 2.2 10 94 0.3 2.1 5 105 0.5 2.2 14 1230.3 2.4 20 151 0.3 2.1 2 159 0.3 2.1 4 161 0.3 2.2 11 183 0.3 2.4 23 2210.3 2.2 12 241 0.3 2.2 8 267 0.3 2.1 3 277 0.3 2.4 18 960 0.0

Test Temperature 350° F.

The loss of fluid from cementing compositions maintained at atemperature of 350° F. was determined for compositions 1-7 (Table 2.1),compositions 19-22 (Table 2.4) and composition 24 (Table 2.5).

Compositions 1, 4, 5 and 6 contained fluid loss additive 1 (FLA-1, Table1.1).

Composition 1, having a fluid loss additive quantity of 1.80 grams (0.3%by weight of cement), experienced a fluid loss of 90 cc per 30 minutes.Composition 4, also having a fluid loss additive quantity of 1.80 (0.3%by weight of cement), experienced a fluid loss of 161 cc per minutes.The difference between compositions 1 and 4 was the use of silica sandin composition 1 versus the use of silica flour in composition 4,together with consequent increase in water requirement for silica flour.

Composition 5, having a fluid loss additive quantity of 3.00 grams (0.5%by weight of cement), experienced a fluid loss of 105 cc per 30 minutes.Composition 6, having a fluid loss additive quantity of 4.20 grams (0.7%by weight of cement), experienced a fluid loss of 68 cc per 30 minutes.The difference between compositions 4, 5 and 6 was the quantity of fluidloss additive. These data illustrate that increase in quantity of fluidloss additive, with all other parameters remaining constant, produces adecrease in fluid loss.

Compositions 2, 3 and 7 contained fluid loss additive 2 (FLA-2, Table1.2).

Composition 2, having a fluid loss additive quantity of 1.8 grams (0.3%by weight of cement), experienced a fluid loss of 159 cc per 30 minutes.Composition 3, also having a fluid loss additive quantity of 1.8 grams(0.3% by weight of cement), experienced a fluid loss of 277 cc per 30minutes. The difference between compositions 2 and 3 was the use ofsilica sand in composition 2 versus the use of silica flour incomposition 3, together with consequent increase in water requirementfor silica flour.

The difference between compositions 1 and 2 was the use of FLA-1 incomposition 1 versus the use of FLA-2 in composition 2. The compositioncontaining FLA-1 produced lower fluid loss than the compositioncontaining FLA-2.

Composition 7, having a fluid loss additive quantity of 4.2 grams (0.7%by weight of cement) experienced a fluid loss of 88 cc per 30 minutes.The difference between compositions 3 and 7 was the quantity of fluidloss additive. These data illustrate that increase in the quantity offluid loss additive, with all other parameters remaining constant,produces a decrease in fluid loss.

The difference between compositions 6 and 7 was the use of FLA-1 incomposition 6 versus the use of FLA-2 in composition 7. The compositioncontaining FLA-1 produced lower fluid loss than the compositioncontaining FLA-2.

Compositions 19, 20, 21 and 22 contained fluid loss additive 3 (FLA-3,Table 1.3).

Composition 19, having a fluid loss additive quantity of 1.80 (0.3% byweight of cement), experienced a fluid loss of 81 and 84 cc per 30minutes. Composition 20, having a fluid loss additive quantity of 1.80grams (0.3% by weight of cement, experienced a fluid loss of 151 cc per30 minutes. The difference between compositions 19 and 20 was the use ofClass H cement in composition 19 and the use of Class G cement incomposition 20, together with consequent increase in water requirementfor use of Class G cement. The composition containing Class H cementproduced lower fluid loss than the composition containing Class Gcement.

Compositions 21 and 22, each had a fluid loss additive content of 3.00grams (0.5% by weight of cement), and each experienced a fluid loss of70 cc per 30 minutes. Compositions 21 and 22 displayed variousdifferences. Composition 21 contained Class G cement and 264 grams ofwater. Composition 22 contained Class H cement, 228 grams of water,41.04 grams of NaCl (18% by weight of water) and 0.6 grams of defoamer.These data illustrate that identical fluid loss can be obtained in saltwater as can be obtained in D.I. water.

The difference between compositions 20 and 21 was the quantity of fluidloss additive. These data illustrate that increase in quantity of fluidloss additive, with all other parameters remaining constant, produces adecrease in fluid loss.

Composition 24, having a fluid loss additive quantity of 3.0 grams (0.5%by weight of cement), experienced a fluid loss of 91 cc per 30 minutes.The difference between composition and composition 24 was the quantityof fluid loss additive. These data illustrate that increase in thequantity of fluid loss additive, with all other parameters remainingconstant, produces a decrease in fluid loss.

Test Temperature 180° F.

The loss of fluid from cementing compositions maintained at atemperature of 180° F. was determined for compositions 8, 9, 10, 11, 12,13 and 14 (Table 2.2), compositions 18, 19, 20, 22 and 23 (Table 2.4)and composition 25 (Table 2.5).

Compositions 8, 9, 10, 11 and 13 each contained 2.55 grams (0.3% byweight of cement) of FLA-1 (Table 1.1). Composition 9 experienced afluid loss of 73 cc per 30 minutes. Composition 13 experienced a fluidloss of 88 cc per 30 minutes. Composition 10 experienced a fluid loss of94 cc per 30 minutes. Composition 11 experienced a fluid loss of 183 ccper 30 minutes. Composition 8 experienced a fluid loss of 267 cc per 30minutes. In general, the fluid loss experienced for each of compositions8, 9, 10, 11 and 13 increased with decrease in dispersant (Table B).Compositions 9 and 13 each contained the same quantity of dispersant,but composition 13 contained a suspension agent while composition 9 didnot include a suspension agent (Table B). Composition 25 contained 4.25grams (0.5% by weight of cement) of FLA-2 (Table 1.2) and experienced afluid loss of 78 cc per 30 minutes.

Composition 8 experienced the highest fluid loss. Composition 8contained no dispersant, no suspension agent and a quantity of set timeretarder greater than the quantity employed in compositions 9, 10, 11and 13.

Compositions 12 and 14 each contained 2.55 grams (0.3% by weight ofcement) of FLA-2 (Table 1.2). Composition 14 experienced a fluid loss of123 cc per 30 minutes. Composition 12 experienced a fluid loss of 241 ccper 30 minutes. The fluid loss experienced for compositions 12 and 14increased with decrease in dispersant (Table B).

The difference between compositions 11 and 12 resided in the presence ofFLA-1 in composition 11 and FLA-2 in composition 12. The fluid lossexperienced for composition 11 was less than that experienced forcomposition 12. Accordingly, the composition containing FLA-1 producedlower fluid loss than the composition containing FLA-2.

The difference between compositions 14 and 25 was the quantity of fluidloss additive. These data illustrate that increase in the quantity offluid loss additive, with all other parameters remaining constant,produces a decrease in fluid loss.

Compositions 19, 20, 22 and 23 contained fluid loss additive 3 (FLA-3,Table 1.3). Compositions 19, 20 and 23 each contained 1.80 grams (0.3%by weight of cement) of fluid loss additive. Composition 22 contained3.00 grams (0.5% by weight of cement) of FLA-3 (Table 1.3). Composition19 experienced a fluid loss of 80 cc per 30 minutes. Composition 20experienced a fluid loss of 62 cc per 30 minutes. Composition 23experienced a fluid loss of 221 cc per 30 minutes. Composition 22experienced a fluid loss of 53 cc per 30 minutes.

The difference between compositions 19 and 20 was the use of Class Hcement in composition 19 and the use of Class G cement in composition 20and an increase in water content. Composition 19, containing Class Hcement, produced higher fluid loss than composition 20, containing ClassG cement.

The difference between compositions 20 and 23 was the use in composition23 of Class H cement, 84.7 grams of NaCl (37.15% by weight of water) and0.6 grams of defoamer, and the use in composition 20 of Class G cementand an increase in water content. Composition 23, containing Class Hcement, salt and defoamer, produced higher fluid loss than composition20, containing Class G cement but no salt and no defoamer.

The difference between compositions 19 and 23 was the use in composition23 of 84.7 grams of NaCl (37.15% by weight of water) and 0.6 grams ofdefoamer. Composition 19 produced lower fluid loss than composition 23.

The difference between compositions 19 and 22 was the use in composition22 of 3.0 grams of FLA-3 (0.5% by weight of cement), 41.04 grams of NaCl(18% by weight of water) and 0.6 grams of defoamer. Composition 19produced higher fluid loss than composition 22. More fluid loss additivein composition 22 produced lower fluid loss.

Test Temperature 80° F.

The loss of fluid from cementing compositions maintained at atemperature of 80° F. was determined for compositions 15, 16 and 17(Table 2.3) and composition 26 (Table 2.5).

Composition 15 contained 2.89 grams (0.34% by weight of cement) of fluidloss additive (FLA-1, Table 1.1). Composition 15 experienced a fluidloss of 40 cc per 30 minutes.

Each of compositions 16 and 17 contained 2.89 grams (0.34% by weight ofcement) of fluid loss additive 2 (FLA-2, Table 1.2). Composition 26contained 4.25 grams (0.5% by weight of cement) of fluid loss additive 2(FLA-2, Table 1.2). Composition 16 experienced a fluid loss of 53 cc per30 minutes. Composition 17 experienced a fluid loss of 78 cc per 30minutes. Composition 26 experienced a fluid loss of 37 cc per 30minutes.

Composition 15, containing FLA-1, produced lower fluid loss thancompositions 16 and each of which contained FLA-2. Furthermore,composition 17, which also contained a suspension agent, produced ahigher fluid loss than composition 16 which did not contain a suspensionagent.

The difference between compositions 16 and 26 was the quantity of fluidloss additive. These data illustrate that increase in the quantity offluid loss additive, with all other parameters remaining constant,produces a decrease in fluid loss.

Fluid Properties (Rheology) Tests . . . Experimental Procedure

Cement slurries were prepared and conditioned as previously described inconnection with the above described Fluid Loss Tests.

The elapsed time between completion of slurry conditioning and rheologytesting was less than 1 minute.

The conditioned slurry was processed in an OFITE Model 800 viscometeravailable from OFI Testing Equipment, Inc., of Houston, Tex., whereinthe slurry was poured into the cup of the viscometer to depth of themark fixed on the cup.

The filled viscometer cup was placed on the viscometer platform andraised to the prescribed level on the sleeve attached to the viscometer.The sleeve was caused to rotate around the bob at 300 rpm for 60 secondsbefore the first dial reading was recorded.

Additional rotational measurements were taken in the order of 200 rpm,100 rpm, 6 rpm and 3 rpm. Each additional rotation extended for 20seconds. Dial readings after each 20 second rotation were recorded.

Fluid Properties Test Results Table 3.2

Table 3.2 contains results of fluid properties tests conducted on 15cementing compositions.

TABLE 3.2 Atmospheric Rheology Data Fluid Fluid Consistency 180° F. LossLoss ABc rpm Solids TABLE COMP. FLA 350° F. 180° F. initial 20 min 300200 100 6 3 Suspension 2.4 22 3 70 53 24 15 256 188 114 19 12 Excellent2.4 19 3 84/81 80 21 15 253 187 116 22 14 Excellent 2.1 1 1 90 21 16 221161 94 11.5 7 Excellent 2.1 6 1 68 — — 214 153 86 9.5 5.5 Excellent 2.12 2 159 15 9 176 124 72 9.5 5.5 Excellent 2.4 20 3 151 62 13 10 163 12075 14 10 Excellent 2.2 8 1 267 7 10 157 123 82 26 25 Excellent 2.4 23 3221 27 10 125 86 47 5 3 — 2.2 13 1 88 10 9 120 87 52 8 5 Excellent 2.418 — 960 14 10 111 81 53 16 12 Excellent 2.2 11 1 183 6 6 102 74 44 8 8Excellent 2.2 14 2 123 9 8 87 62 37 5 3.5 Acceptable 2.2 10 1 94 6 4 6445 24 2.5 2 Some Compacted Solids 2.2 12 2 241 6 4 61 41 22 2 1.5Settled Solids 2.2 9 1 73 6 5 59 41 22 2 1.5 Compacted Solids

Rheology tests were conducted on compositions 1, 2 and 6 (Table 2.1);compositions 8, 9, 10, 11, 12, 13 and 14 (Table 2.2); and compositions18, 19, 20, 22 and 23 (Table 2.4). The tests were conducted at atemperature of 180° F.

Compositions 1, 6, 8, 9, 10, 11 and 13 contained fluid loss additive 1(FLA 1, Table 1.1). Composition 2, 12 and 14 contained fluid lossadditive 2 (FLA 2, Table 1.2). Compositions 19, 20, 22 and 23 containedfluid loss additive 3 (FLA 3, Table 1.3). Composition 18 did not containa fluid loss additive.

Conditioning treatments were performed on compositions 1 and 2 (Table2.1) and on compositions 8, 9, 10, 11, 12, 13 and 14 (Table 2.2).

All compositions tested, other than compositions 9, 10, 12 and 14, wereclassified as having “excellent” solids suspension properties. Thecompositions having the excellent rating all had rheology dial readingsof at least 100 at 300 rpm.

Compositions 1, 6, 19 and 22 were each rated as having excellent solidssuspension properties, and each experienced less than 100 cc fluid lossper 30 minutes at 350° F. In addition, each of these compositionscontained a fluid loss additive copolymer in which maleic anhydride wasincluded as a reactant. Also, composition 22 contained 18% NaCl byweight of water.

Fluid Properties Test Results Table 3.3

Table 3.3 contains results of fluid properties tests conducted on 3cementing compositions.

Rheology tests were conducted on compositions 15, 16 and 17 (Table 2.3).The tests were conducted at a temperature of 80° F.

Composition 15 contained fluid loss additive 1 (FLA-1, Table 1.1).Compositions 16 and contained fluid loss additive 2 (FLA-2, Table 1.2).

TABLE 3.3 Fluid Rheology Data 80° F. Loss rpm Solids TABLE COMP FLA 80°F. 300 200 100 6 3 Suspension 2.3 15 1 40 148 103 55 5 3 Good 2.3 17 278 138 98 55 5.5 3.5 Good 2.3 16 2 53 108 74 39 2.5 2 Compacted Solids

Compositions 15 and 17 were classified as having “good” solidssuspension properties. The compositions having the good rating all hadrheology dial readings of at least 135 at 300 rpm.

Composition 15, having the lowest fluid loss and the highest rheologydial reading, contained a fluid loss additive copolymer in which maleicanhydride was included as a reactant.

Compositions 15 and 17 experienced similar suspension properties. Thedial reading of composition 15 was higher than that for composition 17(Table 3.3). The fluid loss additive in composition 15 did containmaleic anhydride, composition 17 did not contain maleic anhydride. Thefluid loss experienced with composition 17 was greater than that forcomposition 15 (Table 3.1).

Each composition tested contained the same quantity of fluid lossadditive, but neither of compositions 16 or 17 contained a fluid lossadditive copolymer in which maleic anhydride was included as a reactant.

The difference between compositions 16 and 17 was the use in composition17 of a suspension agent together with consequent increase in waterrequirement. Composition 16 experienced compacted solids.

Example 4

Hydraulic cementing compositions of this invention containing fluid lossadditive composition 1 (Table 1.1) were tested to determine zero geltime and transition time.

The tests were performed by employing model 5265 SGSA static gelstrength analyzer available from Chandler Engineering, of Broken Arrow,Okla. The results of the tests are provided in Table 4.

The cement slurries to be tested were prepared and then immediatelytreated in an atmospheric consistometer at 80° F. for 20 minutes. Themethods of slurry preparation and conditioning are described above.

Immediately after conditioning, the gel strength developed by eachslurry after 10 minutes was determined by permitting a portion of theslurry to remain static for 10 minutes and then, by using a rotationalviscometer, recording the maximum deflection at 3 rpm followed by oneminute of stirring at 300 rpm. The instrument dial reading, in lbs/100ft², at the termination of the 300 rpm stirring was the initial gelstrength in the SGSA test.

During the above mentioned 10 minute static period, the remainingportion of the conditioned slurry was poured into the cup of the SGSAcell to the appropriate level, the cell was filled with water and thenclosed.

The SGSA test was initiated at 80° F. and 3000 psi immediately followingthe conclusion of the above mentioned 10 minute static period. Whilemaintaining pressure at 3000 psi the test temperature was maintained at80° F. for the duration of the test period. In another test, the initialtemperature of 80° F. was increased to 250° F. after 60 minutes andmaintained at that temperature for the duration of the test. In anothertest, the initial temperature of 80° F. was increased to 350° F. after75 minutes and maintained at that temperature for the duration of thetest.

Zero gel time was calculated by the SGSA device. Transition time was thetime required for gel strength to increase from 100 lb/100 ft² to 500lb/100 ft².

TABLE 4 ZERO GEL TIME and TRANSITION TIME FLA-1 pounds per Test Zero GelTransition Cement 100 pounds Temperature Time Time Composition drycement F.° hours hours  1 0.3 350 11.25  0.28 27 0.5 250 6.08 0.53 280.8 250 8.02 0.23 15 0.34  80 6.97 0.73

Composition 1 (Table 2.1) contained Class H cement, FLA-1 (Table 1.1),silica sand, a set time retarder, a retarder intensifier, and asuspension agent.

Compositions 27 and 28 (Table 2.5) each contained Class H cement, FLA-1,silica flour, a set time retarder, and a retarder intensifier.Composition 28 contained a greater amount of fluid loss additive thancomposition 27.

Composition 15 (Table 2.3) contained Class H cement and FLA-1.

Having described the invention, that which is claimed is:
 1. A method ofmaking a fluid loss additive useful to reduce the loss of fluid from aslurry of a cementing composition in water, said method comprising thesteps of: preparing a first aqueous medium comprised of water and ahumate, adding a first compound, a second compound and a third compoundto said first aqueous medium to produce a combination and adjusting thepH of said combination to a value greater than 7 to thereby form asecond aqueous medium, heating said second aqueous medium to a reactiontemperature, adding activator ingredients to said second aqueous mediumto form a reaction mass and to commence polymerization reaction, saidactivator ingredients being comprised of a chain transfer agent and apolymerization initiator, and permitting said polymerization reaction toproceed for a suitable period of time to thereby produce an aqueoussolution containing said fluid loss additive; Wherein: said firstcompound is the sodium salt of 2-acrylamido-2-methylpropanesulphonicacid, said second compound is N,N-dimethylacrylamide, and said thirdcompound is maleic anhydride; the mole ratio of said first compound tosaid second compound in said fluid loss additive is an amount in therange of from about 1.5 to about 2.5 moles of said first compound permole of said second compound; and the mole ratio of said first compoundto said third compound in said fluid loss additive is an amount in therange of from about 4.8 to about 9.8 moles of said first compound permole of said third compound.
 2. The method of claim 1 wherein saidaqueous solution containing said fluid loss additive is dried to producea dry polymer product consisting essentially of said fluid lossadditive.
 3. A method of making a fluid loss additive useful to reducethe loss of fluid from a slurry of a cementing composition in water,said method comprising the steps of: preparing a first aqueous mediumcomprised of water and a humate, adding a first compound, a secondcompound and a third compound to said first aqueous medium to produce acombination and adjusting the pH of said combination to a value greaterthan 7 to thereby form a second aqueous medium, heating said secondaqueous medium to a reaction temperature, adding activator ingredientsto said second aqueous medium to form a reaction mass and to commencepolymerization reaction, said activator ingredients being comprised of achain transfer agent and a polymerization initiator, and permitting saidpolymerization reaction to proceed for a suitable period of time tothereby produce an aqueous solution containing said fluid loss additive;Wherein: said first compound is a sulfonic acid acrylic monomer havingthe general formulaCH₂═CH₁—C(═O)—NR₂R₃ wherein R₁ is —H or —CH₃; R₂ is —H, —CH₃ or —CH₂CH₃;and R₃ is —C(CH₃)₂—CH₂—S(═O)₂—OX, wherein X is —H, —NH₄ or a Group 1Ametal; said second compound is selected from an acrylamide monomerhaving the general formulaCH₂═CR₄—C(═O)—NR₅R₆ wherein R₄ is —H or —CH₃; R₅ is —H, —CH₃ or —CH₂CH₃;and R₆ is —H, —CH₃, —CH₂CH₃, —CH(CH₃)₂ or —C(CH₃)₃; and said thirdcompound is an ethylene monomer having the general formulaR₉R₁₁C═CR₁₀R₁₂ wherein R₉ is —C(═O)OH, —C(═O)ONa, —CH₂C(═O)OH or —H; R₁₀is, —C(═O)OH or —H; R₁₁ is —C(═O)OH or —H and R₁₂ is —H; or R₉ and R₁₀are each carbonyl groups joined to oxygen to form an anhydride group,—C(═O)—O—C(═O)—; the mole ratio of said first compound to said secondcompound in said fluid loss additive is an amount in the range of fromabout 1.5 to about 2.5 moles of said first compound per mole of saidsecond compound; and the mole ratio of said first compound to said thirdcompound in said fluid loss additive is an amount in the range of fromabout 4.8 to about 9.8 moles of said first compound per mole of saidthird compound.
 4. The method of claim 3 wherein said first compound isselected from 2-acrylamido-2-methylpropanesulphonic acid and the sodiumand ammonium salts thereof; said second compound is selected fromacrylamide, methacrylamide, N-methylacrylamide, N-i-propylacrylamide,N-i-propylmethacrylamide, N-t-butylacrylamide, N-t-butylmethacrylamide,N,N-dimethylacrylamide, and N,N-dimethylmethacrylamide; and said thirdcompound is selected from maleic acid, fumaric acid, itaconic acid andmaleic anhydride.
 5. The method of claim 4 wherein said aqueous solutioncontaining said fluid loss additive is dried to produce a dry polymerproduct consisting essentially of said fluid loss additive.